java.lang.IllegalArgumentException: Unable to create call adapter for interface retrofit.Call

Question

The code in my VSApiEndpointInterface

@POST(REGISTER_USER)
Call registerUser(@Body User user);

The class of user looks like as below.

public class User {
    String email;
    String password;

    public User(String email, String password) {
        this.email = email;
        this.password = password;
    }
}

In main Activity, I make object of user,

User user = new User("[email protected]", "123456");


Call call = apiService.registerUser(user);
                call.enqueue(new Callback<User>() {
                    @Override
                    public void onResponse(Response<User> response, Retrofit retrofit) {
                        int statusCode = response.code();
                        System.out.print("Veer " +response.body());
                    }

                    @Override
                    public void onFailure(Throwable t) {
                        // Log error here since request failed
                    }
                });

I also tried,

Call<User> registerUser(@Body User user);

But same error.

FULL TRACK

   11-29 10:12:59.299 28854-28854/com.myapp.app W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x41017258)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime: FATAL EXCEPTION: main
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime: java.lang.IllegalArgumentException: Unable to create call adapter for interface retrofit.Call
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     for method VSApiEndpointInterface.registerUser
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Utils.methodError(Utils.java:177)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.MethodHandler.createCallAdapter(MethodHandler.java:47)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.MethodHandler.create(MethodHandler.java:26)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit.loadMethodHandler(Retrofit.java:151)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit$1.invoke(Retrofit.java:132)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at $Proxy0.registerUser(Native Method)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.myapp.app.activity.LoginActivity$1.onClick(LoginActivity.java:48)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.view.View.performClick(View.java:3517)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.view.View$PerformClick.run(View.java:14155)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:605)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:92)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:4508)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:  Caused by: java.lang.IllegalArgumentException: Call return type must be parameterized as Call<Foo> or Call<? extends Foo>
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Utils.getCallResponseType(Utils.java:185)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.ExecutorCallAdapterFactory.get(ExecutorCallAdapterFactory.java:35)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit.nextCallAdapter(Retrofit.java:189)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit.callAdapter(Retrofit.java:175)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.MethodHandler.createCallAdapter(MethodHandler.java:45)
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.MethodHandler.create(MethodHandler.java:26) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit.loadMethodHandler(Retrofit.java:151) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at retrofit.Retrofit$1.invoke(Retrofit.java:132) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at $Proxy0.registerUser(Native Method) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.myapp.app.activity.LoginActivity$1.onClick(LoginActivity.java:48) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.view.View.performClick(View.java:3517) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.view.View$PerformClick.run(View.java:14155) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:605) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:92) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:4508) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576) 
    11-29 10:12:59.326 28854-28854/com.myapp.app E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 

I want to know my mistake in code. secondly reason of error.

Thanks.

Answer 1

I had the same problem. It was working in debugging mode and was failing on release mode.

The problem was because of the pro-guard rules.

This is what helped me https://github.com/krschultz/android-proguard-snippets/tree/master/libraries

Retrofit and Okio rules from here worked for me.

Answer 2

add these to pro-guard rules

-keepattributes Signature
-keep class com.google.gson.reflect.TypeToken { *; }
-keep class * extends com.google.gson.reflect.TypeToken
-keepattributes AnnotationDefault,RuntimeVisibleAnnotations
-keep,allowobfuscation,allowshrinking interface retrofit2.Call
-keep,allowobfuscation,allowshrinking class retrofit2.Response
-keep,allowobfuscation,allowshrinking class kotlin.coroutines.Continuation
-dontwarn okhttp3.internal.platform.**
-dontwarn org.conscrypt.**
-dontwarn org.bouncycastle.**
-dontwarn org.openjsse.**
-keep class retrofit2.** { *; }
-keep class okhttp3.** { *; }
-keep class com.google.gson.** { *; }
-keepattributes *Annotation*
-dontwarn sun.misc.**
-keep class com.google.gson.examples.android.model.** { *; }
-keep class * implements com.google.gson.TypeAdapterFactory
-keep class * implements com.google.gson.JsonSerializer
-keep class * implements com.google.gson.JsonDeserializer
# JSR 305 annotations are for embedding nullability information.
-dontwarn javax.annotation.**
# A resource is loaded with a relative path so the package of this class must be preserved.
-adaptresourcefilenames okhttp3/internal/publicsuffix/PublicSuffixDatabase.gz
# Animal Sniffer compileOnly dependency to ensure APIs are compatible with older versions of Java.
-dontwarn org.codehaus.mojo.animal_sniffer.*
# OkHttp platform used only on JVM and when Conscrypt and other security providers are available.
-keepattributes Annotation
-keep interface okhttp3.** { *; }
-dontwarn okhttp3.**
-dontwarn okio.**
-dontwarn org.conscrypt.*